Add locale parsing

locale/locale.go

@@ -0,0 +1,68 @@
+// Package locale defines a Locale type that represents a POSIX locale value, as
+// required by desktop-entry-spec.
+package locale
+
+import "fmt"
+import "strings"
+
+type localeError string
+func (err localeError) Error () string { return string(err) }
+
+const (
+	// ErrUnexpectedRune indicates an unexpected rune was encountered while
+	// parsing a locale string.
+	ErrUnexpectedRune = localeError("unexpected rune")
+	// ErrLangEmpty indicates that a lang value was not specified.
+	ErrLangEmpty = localeError("lang empty")
+)
+
+// Locale represents a POSIX locale value.
+type Locale struct {
+	Lang     string
+	Country  string
+	Encoding string
+	Modifier string
+}
+
+// String returns the string representation of the Locale. Unspecified values
+// are left out.
+func (locale Locale) String () string {
+	str := locale.Lang
+	if locale.Country != "" {
+		str = fmt.Sprint(str, "_", locale.Country)
+	}
+	if locale.Encoding != "" {
+		str = fmt.Sprint(str, ".", locale.Encoding)
+	}
+	if locale.Modifier != "" {
+		str = fmt.Sprint(str, "@", locale.Modifier)
+	}
+	return str
+}
+
+// Parse parses a formatted locale string and returns the corresponding Locale.
+func Parse (value string) (Locale, error) {
+	locale := Locale { }
+	value, locale.Modifier, _ = strings.Cut(value, "@")
+	value, locale.Encoding, _ = strings.Cut(value, ".")
+	value, locale.Country,  _ = strings.Cut(value, "_")
+	locale.Lang = value
+
+	if hasIllegalRunes(locale.Lang) ||
+		hasIllegalRunes(locale.Country) ||
+		hasIllegalRunes(locale.Encoding) ||
+		hasIllegalRunes(locale.Modifier) {
+		
+		return Locale { }, ErrUnexpectedRune
+	}
+
+	if locale.Lang == "" {
+		return Locale { }, ErrLangEmpty
+	}
+	
+	return locale, nil
+}
+
+func hasIllegalRunes (value string) bool {
+	return strings.ContainsAny(value, "@._ ")
+}

locale/locale_test.go

@@ -0,0 +1,106 @@
+package locale
+
+import "testing"
+
+func TestString (test *testing.T) {
+	testCase := func (correct string, locale Locale) {
+		got := locale.String()
+		if got != correct {
+			test.Fatalf("expected:\n\t%s\ngot:\n\t%s\n", correct, got)
+		}
+	}
+
+	testCase("lang_COUNTRY.ENCODING@MODIFIER", Locale {
+		Lang:     "lang",
+		Country:  "COUNTRY",
+		Encoding: "ENCODING",
+		Modifier: "MODIFIER",
+	})
+	testCase("lang.ENCODING@MODIFIER", Locale {
+		Lang:     "lang",
+		Encoding: "ENCODING",
+		Modifier: "MODIFIER",
+	})
+	testCase("lang_COUNTRY@MODIFIER", Locale {
+		Lang:     "lang",
+		Country:  "COUNTRY",
+		Modifier: "MODIFIER",
+	})
+	testCase("lang_COUNTRY.ENCODING", Locale {
+		Lang:     "lang",
+		Country:  "COUNTRY",
+		Encoding: "ENCODING",
+	})
+	testCase("lang_COUNTRY", Locale {
+		Lang:     "lang",
+		Country:  "COUNTRY",
+	})
+	testCase("lang.ENCODING", Locale {
+		Lang:     "lang",
+		Encoding: "ENCODING",
+	})
+	testCase("lang@MODIFIER", Locale {
+		Lang:     "lang",
+		Modifier: "MODIFIER",
+	})
+}
+
+func TestParse (test *testing.T) {
+	testCase := func (input string, correct Locale) {
+		got, err := Parse(input)
+		if err != nil {
+			test.Fatal(err)
+		}
+		if got != correct {
+			test.Fatalf("expected:\n\t%v\ngot:\n\t%v\n", correct, got)
+		}
+	}
+
+	testCase("lang_COUNTRY.ENCODING@MODIFIER", Locale {
+		Lang:     "lang",
+		Country:  "COUNTRY",
+		Encoding: "ENCODING",
+		Modifier: "MODIFIER",
+	})
+	testCase("lang.ENCODING@MODIFIER", Locale {
+		Lang:     "lang",
+		Encoding: "ENCODING",
+		Modifier: "MODIFIER",
+	})
+	testCase("lang_COUNTRY@MODIFIER", Locale {
+		Lang:     "lang",
+		Country:  "COUNTRY",
+		Modifier: "MODIFIER",
+	})
+	testCase("lang_COUNTRY.ENCODING", Locale {
+		Lang:     "lang",
+		Country:  "COUNTRY",
+		Encoding: "ENCODING",
+	})
+	testCase("lang_COUNTRY", Locale {
+		Lang:     "lang",
+		Country:  "COUNTRY",
+	})
+	testCase("lang.ENCODING", Locale {
+		Lang:     "lang",
+		Encoding: "ENCODING",
+	})
+	testCase("lang@MODIFIER", Locale {
+		Lang:     "lang",
+		Modifier: "MODIFIER",
+	})
+}
+
+func TestParseErr (test *testing.T) {
+	testCase := func (input string, correct error) {
+		_, err := Parse(input)
+		if err != correct {
+			test.Fatalf("expected:\n\t%v\ngot:\n\t%v\n", correct, err)
+		}
+	}
+
+	testCase("lang.ENCODING.MODIFIER", ErrUnexpectedRune)
+	testCase("lang@COUNTRY.ENCODING", ErrUnexpectedRune)
+	testCase("lang.@COUNTRY.ENCODING", ErrUnexpectedRune)
+	testCase("_COUNTRY.ENCODING@MODIFIER", ErrLangEmpty)
+}